The move indicates an expansion of a clampdown on "immoral" conduct launched last year against women flouting rules to cover their heads and disguise the shape of their bodies in public, in line with Iran's Islamic system.

"In the first stage, police will only confront companies ... that are active in small buildings or complexes," the head of the moral security police, Ahmad Rouzbehani, was quoted as saying.

Mehr said the move was "to prevent social damage" and the hijab, or veil, "should be respected". It said the campaign would start from around May 4.

Iran's religious codes require women to cover their hair and wear long, loose clothing to disguise their bodies in public, including offices where they may work with male colleagues.

Police sometimes check offices to ensure the codes are upheld and can shut them down. Some coffee shops have been closed after police said workers or customers were not meeting standards.

Restaurants and other public places often have signs asking customers to respect the Islamic Republic's dress requirements.

The enforcement of "hijab" has been a cornerstone of the Islamic system introduced after the 1979 revolution.

The crackdown against what clerics see as "corrupt" Western influence coincides with rising pressure on Iran by the West over its nuclear program. The United States and its allies say Iran wants to build an atomic bomb, which Tehran denies.

"Everybody, both women and men, just as they want financial and physical security, like to have moral security," Rouzbehani said, adding that police had urged people "to come forward with their reports".

In the past, crackdowns tended to be launched at the start of Iran's hot summers and petered out soon after. But last year's extended into winter and included a drive against tight women's trousers and even men with spiky "Western" hairstyles.

Those who violate dress codes are usually cautioned on a first offence, sometimes after a brief visit to a police station. But they can be held for longer, taken to court and required to have "guidance classes" after repeat offences.

Dress codes are most often flouted in wealthier, urban areas. Conservative dress is the norm in poorer, rural areas.